The family consists of a single genus, Fissidens Hedw., six subgenera, and approximately 500 species worldwide. Not all subgenera are represented in Central America. Fissidens hyalinus, F. juruensis var. juruensis, and F. cylindraceus have not been reported from Central America, but are included in the key since they are likely to be encountered.

Plants aquatic, lignicolous, saxicolous, or terrestrial, small to large, 1 mm to 8 cmor more in length, unbranched or branched; stem with or without a central strand; axillary hyaline nodules present or absent; rhizoids basal or axillary, smooth or papillose. Leaves distichous and equitant, each differentiated into two vaginant laminae that clasp the stem, a dorsal lamina and a ventral lamina; costa single (nearly lacking in a few species), ending well below the leaf apex to excurrent; cells 1(–2)-stratose (multistratose in a few species), irregularly hexagonal to rounded, isodiametric to elongate, sometimes guttulate (small, clear, drop-like areas in cells), smooth, mammillose, unipapillose or pluripapillose, sometimes much elongated and thick-walled at the margins (infrequently submarginal) and forming uni- to multistratose limbidia on all laminae or portions thereof. Monoicous, synoicous or dioicous; perichaetial and perigonial leaves often differentiated; paraphyses lacking. Sporophytes terminal on stems and branches, often appearing lateral or basal, 1(–2, infrequently more) per perichaetium. Setae mostly elongate (immersed to very short in some species of subgenera Octodiceras and Sarawakia); capsules erect or inclined, symmetric to somewhat arcuate; annuli none; peristome haplolepideous (absent in a few species), teeth typically divided to below the middle, sometimes divided irregularly or undivided, red to red-brown, spirally thickened or articulate above, smooth to papillose to striolate or ridged below; opercula conic to long-rostrate from a conic base. Spores smooth to finely papillose. Calyptrae cucullate or mitrate, smooth or papillose.